Purification of human interleukin 1

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Interleukin-1 (IL-1) is a crucial lymphocyte stimulant produced by human monocytes.
• IL-1 exists in both low molecular weight (approx. 13,000) and high molecular weight (approx. 85,000) forms.
• The high molecular weight form may arise from complexes with serum components during culture or purification.

Purpose of the Study:

• To purify and characterize human Interleukin-1 (IL-1).
• To investigate the molecular properties and biological activity of purified IL-1.
• To assess the minimum quantity of IL-1 required for biological activity.

Main Methods:

• Monocyte culture with lipopolysaccharide (LPS) to induce IL-1 production.
• Purification techniques including hollow fiber diafiltration and membrane ultrafiltration.
• Isoelectric focusing (IEF) followed by polyacrylamide gel electrophoresis (PAGE) with sensitive protein staining.

Main Results:

• Separation of low molecular weight IL-1 achieved with 4% yield using membrane filtration.
• Recovery of high molecular weight IL-1 (21% yield) containing serum proteins.
• Highly purified IL-1 via IEF/PAGE showed trace immunoglobulin but no other protein bands, despite significant biological activity.

Conclusions:

• Human IL-1 exhibits potent biological activity at picogram levels.
• The purification process can yield highly pure IL-1, though challenges with high molecular weight forms exist.
• Sensitive detection methods are crucial for characterizing biologically active molecules present in minute quantities.